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PubMed1996

Fatigue strength of polyethylene after sterilization by gamma irradiation or ethylene oxide.

The oxidation level of ultrahigh molecular weight polyethylene specimens sterilized by gamma irradiation in either air or Ar gas was compared with that of unsterilized and ethylene oxide sterilized ultrahigh molecular weight polyethylene. The fatigue strength of ultrahigh molecular weight polyethylene specimens sterilized by gamma irradiation in air was compared with that of unsterilized and ethylene oxide sterilized ultrahigh molecular weight polyethylene. At the specimen surface, oxidation was highest for ultrahigh molecular weight polyethylene gamma irradiated in air, lower for ultrahigh molecular weight polyethylene gamma irradiated in Ar gas, and absent in unsterilized and ethylene oxide sterilized ultrahigh molecular weight polyethylene. At a depth of 3.5 mm below the specimen surface, oxidation levels were equivalent for ultrahigh molecular weight polyethylene gamma irradiated in either air or Ar gas whereas unsterilized and ethylene oxide sterilized specimens were again unoxidized. Thus, even in an inert atmosphere, oxidative degradation of gamma irradiated ultrahigh molecular weight polyethylene occurs. The 10 million cycle fatigue strength was similar for unsterilized and ethylene oxide sterilized ultrahigh molecular weight polyethylene whereas the fatigue strength of gamma irradiated in air ultrahigh molecular weight polyethylene was lower. Results of this study show that ethylene oxide gas does not degrade ultrahigh molecular weight polyethylene whereas gamma radiation in air causes changes in the polymer that adversely affect its mechanical properties. Ethylene oxide gas is a viable alternative to gamma radiation in air that avoids oxidation and fatigue strength degradation known to accompany irradiation of ultrahigh molecular weight polyethylene polymer bearing surfaces in total joint implants.

Biophysical Phenomena↗

PubMed2003

Effect of radiation, heat, and aging on in vitro wear resistance of polyethylene.

Radiation cross-linking increases the wear resistance of polyethylene used in total hip replacement. Radiation also generates residual free radicals, which are detrimental to long-term properties of polyethylene. Two approaches are used to stabilize the residual free radicals and terminally sterilize the components. One is postirradiation annealing with gas sterilization and the other is postirradiation melting with gamma sterilization in nitrogen. The hypothesis of the current study is that postirradiation annealing followed by gamma sterilization in nitrogen will result in more free radicals in polyethylene than gamma sterilization either in air or in nitrogen alone. To test this hypothesis, concentration of residual free radicals was quantified in polyethylene that was annealed and gamma sterilized in nitrogen and control polyethylenes gamma sterilized in air versus in nitrogen. Three crosslinked polyethylenes that were melted and gas sterilized also were included in the study. The effects of residual free radicals were studied by accelerated aging. Oxidation levels and weight loss in bidirectional pin-on-disk tests were determined before and after aging. Polyethylene that was subjected to postirradiation annealing and gamma sterilization resulted in 58% more residual free radicals than control polyethylenes. Weight loss of the annealed polyethylene increased by 16-fold on accelerated aging and had three times higher oxidation levels than that measured in control polyethylenes after aging. In contrast, polyethylenes that were stabilized with postirradiation melting and terminally gas sterilized showed no detectable residual free radicals. Accelerated aging did not affect the weight loss and oxidation levels of melted polyethylenes.

Free Radicals↗

PubMed2001

Maximizing ultra high molecular weight polyethylene performance in total knee replacement.

The etiology of polyethylene wear following TKR is multifactorial. Factors such as surgical technique, patient selection, and choice of implant design directly impact the polyethylene wear rate. Surgical technique is directly associated with polyethylene wear; particularly the thickness of the polyethylene insert, the postoperative mechanical axis of the limb, and the alignment of the tibial component in the coronal plane. Patient selection is an important determinant of polyethylene wear, as patient body weight and activity level have been shown to correlate with wear rate. Prosthetic design plays a role in polyethylene wear as femoral-tibial contact areas, peak contact forces, and surface topography of the polyethylene are important considerations. The method by which the polyethylene is manufactured and the method of sterilization are also important determinants of polyethylene wear. Wear of polyethylene is one source of particulate debris following TKR. Phagocytosis of the particulate debris by macrophage occurs at the prosthesis-bone interface. The macrophage produces inflammatory mediators in response to the particulate debris. Inflammatory mediators act at the failed interface to effect bone resorption and produce osteolysis. In summary, the surgeon can play a major role in maximizing polyethylene performance in TKR by understanding the multiple factors that contribute to polyethylene wear and taking steps to lessen their effect.

Adult↗

PubMed2004

The Otto Aufranc Award. Highly cross-linked polyethylene in total hip arthroplasty: randomized evaluation of penetration rate in cemented and uncemented sockets using radiostereometric analysis.

The annual wear rate in polyethylene articulations should be 0.1 mm or less to avoid future osteolysis. Highly cross-linked polyethylene shows an 80 to 90% wear reduction in hip simulator testing, but the clinical documentation of this new polyethylene is still inadequate. We evaluated the highly cross-linked polyethylene in two prospective randomized clinical studies. Thirty-two patients (12 men, 20 women; 64 hips) with a median age of 48 years (range, 29-70 years) with bilateral primary or secondary arthrosis of the hip had hybrid total hip arthroplasty with liners made of highly cross-linked polyethylene on one side and conventional polyethylene on the other. Twenty-seven patients in this study have passed 2 years followup. A further group, comprised of 60 patients (61 hips) with a median age of 55 years (range, 35-70 years), was randomized to receive either highly cross-linked polyethylene or conventional cemented all-polyethylene of the same design. Forty-nine of these 60 patients have been observed for 3 years. In both studies all patients received Spectron stems with 28-mm Co-Cr heads. Radiostereometric examinations with the patient supine or standing were done at regular intervals. Wear was measured in the supine position from the first postoperative week, whereas standing examinations were initiated 3 months after the operation. The penetration rate almost was identical in the study and control groups at 6 months after the operation. Thereafter, the penetration rate leveled out in the two groups with highly cross-linked polyethylene. At 2 years the highly cross-linked polyethylene liner showed 62% lower proximal penetration and 31% lower total (three-dimensional) penetration when the patients were examined in supine position. The highly crosslinked all-polyethylene cemented cups showed lower proximal penetration in both positions. The better wear performance of highly cross-linked polyethylene could increase the implant longevity. Longer followup is needed to evaluate if this new material is associated with less occurrence of osteolysis.

Adult↗

PubMed2001

Effect of counterface roughness on the wear of conventional and crosslinked ultrahigh molecular weight polyethylene studied with a multi-directional motion pin-on-disk device.

The effect of counterface roughness on the wear of conventional gamma-sterilized, and electron-beam-crosslinked ultrahigh molecular weight polyethylene was studied with a circularly translating pin-on-disk device. The counterfaces, CoCr disks, were either polished, or roughened so that they represented the type of roughening and the range of surface roughness values (R(a) = 0.014-0.24 microm) observed in explanted femoral heads of total hip prostheses. The lubricant was diluted calf serum, and the test length 3 million cycles. A total of 24 tests were done. With both types of polyethylene, there was a strong correlation between R(a) and wear factor k. The power equations were k = 5.87 x 10(-5)(R(a))(0.91) for conventional polyethylene (R(2) = 0.94), and k = 7.87 x 10(-5)(R(a))(2.49) for crosslinked polyethylene (R(2) = 0.82). Crosslinking improved wear resistance significantly. The wear of crosslinked polyethylene against the roughest counterfaces was lower than the wear of conventional polyethylene against the polished counterfaces. Against rough counterfaces, the wear of crosslinked polyethylene was an order of magnitude lower than that of conventional polyethylene. On the crosslinked polyethylene pins that were tested against polished counterfaces, remains of original machining marks were still visible after the test. The average size of wear particles produced by both types of polyethylene against rough counterfaces was similar, 0.4 microm, whereas that produced by conventional and crosslinked polyethylene against polished counterfaces was significantly smaller, 0.2 and 0.1 microm, respectively.

Biocompatible Materials↗

PubMed1999

Assessment of polyethylene wear in total hip replacement.

The three-dimensional technique is a method for the measurement of polyethylene wear in patients with total hip joint replacement. Application of image processing technology allows automation of point selection from digital images of radiographs scanned into the computer. Validation of image processing modifications reveals a three-fold increase in accuracy and a 40-fold increase in reproducibility compared with manual input of points from a digitizer during bench testing. A review of three-dimensional technique application to clinical patients gives information on the factors that influence polyethylene wear. Increasing age, activity level, femoral head size, decreasing polyethylene thickness, and insertion of total hip prostheses without cement all increase polyethylene wear. Restoration of femoral offset during total hip replacement seems to decreases polyethylene wear. No apparent difference in polyethylene wear rate could be found between two groups of patients, one group had a stainless steel-polyethylene articulation and the other had a ceramic-polyethylene articulation. Measurement of the serial polyethylene wear of individual patients reveals a high rate of femoral head penetration during the first 2 years after total hip replacement using metal-backed acetabular components inserted without cement. Interpretation of this femoral head penetration as true polyethylene wear may be erroneous, however, because creep of the polyethylene and acetabular liner movement within its metal shell cannot be measured.

Arthroplasty, Replacement, Hip↗

PubMed2002

Polyethylene glycol without electrolytes for children with constipation and encopresis.

BACKGROUND: Children with functional constipation and encopresis benefit from behavior modification and from long-term laxative medication. Polyethylene glycol without electrolytes has become the first option for many pediatric gastroenterologists. METHODS: Twenty-eight children treated with polyethylene glycol without electrolytes were compared with 21 children treated with milk of magnesia to evaluate the efficiency, acceptability, side effects, and treatment dosage of polyethylene glycol in long-term treatment of functional constipation and encopresis. Children were rated as "doing well," "improved," or "not doing well," depending on resolution of constipation and encopresis. RESULTS: At the 1-, 3-, 6-, and 12-month follow-ups, bowel movement frequency increased and soiling frequency decreased significantly in both groups. At the 1-month follow-up, children on polyethylene glycol were soiling more frequently (P < 0.01) and fewer were improved (P < 0.01). At the 3- and 6-month follow-ups, both groups had similarly improved. At the 12-month visit, 61% of children on polyethylene glycol and 67% of children on milk of magnesia were doing well. Children on polyethylene glycol soiled more frequently (P < 0.01). None refused polyethylene glycol, but 33% refused to take milk of magnesia. The mean initial treatment dosage of polyethylene glycol was 0.6 +/- 0.2 g/kg daily. Polyethylene glycol had no taste, and no loss of efficacy occurred. Polyethylene glycol did not cause clinically significant side effects. CONCLUSIONS: Polyethylene glycol without electrolytes is an alternative for long-term management of children with constipation and encopresis.

Adolescent↗

PubMed2004

Wear, debris, and biologic activity of cross-linked polyethylene in the knee: benefits and potential concerns.

Cross-linked polyethylene currently is being introduced in knee prostheses. The wear rates, wear debris, and biologic reactivity of non cross-linked, moderately cross-linked, and highly cross-linked polyethylene have been compared in multidirectional wear tests and knee simulators. Multidirectional pin-on-plate wear studies of noncross-linked, moderately cross-linked (5 Mrad), and highly cross-linked (10 Mrad) polyethylene showed a 75% reduction in wear with the highly cross-linked material under kinematics found in the hip, but only a 33% reduction under wear in kinematics representative of the knee. In knee simulator studies, with the fixed-bearing press-fit, condylar Sigma cruciate-retaining knee under high kinematic input conditions, the wear of 5 Mrad moderately cross-linked polyethylene was 13 +/- 4 mm per 1 million cycles, which was lower (p < 0.05) than the wear of clinically used, gamma vacuum foil GUR 1020 polyethylene (23 +/- 6 mm/1 million cycles). For the low-contact stress mobile-bearing knee, the wear of moderately cross-linked polyethylene was 2 +/- 1 mm per 1 million cycles, which was lower (p < 0.05) than GVF GUR 1020 polyethylene (5 +/- 2 mm/1 million cycles). The wear debris isolated from the fixed-bearing knees showed the moderately cross-linked material had a larger percentage volume of particles smaller than 1 mum in size, compared with GVF GUR 1020 polyethylene. Direct cell culture studies of wear debris generated in sterile wear simulators using multidirectional motion showed a increase (p < 0.05) in tumor necrosis factor-alpha levels and reactivity for GUR 1050 cross-linked polyethylene debris compared with an equivalent volume of noncross-linked GUR 1050 polyethylene. The use of cross-linked polyethylene in the knee reduces the volumetric wear rate. However, the clinical significance of reduced fracture toughness, elevated wear in abrasive conditions, and the elevated tumor necrosis factor-alpha release from smaller more reactive particles warrant further investigation.

Analysis of Variance↗

PubMed2006

Polyethylene sterilization and production affects wear in total hip arthroplasties.

Production and package sterilization techniques for the polyethylene used in acetabular components for total hip arthroplasties are known to affect wear. We considered three combinations of techniques: sterilization by radiation in inert gas with isostatically molded polyethylene, in inert gas and ram-extruded polyethylene, and in air with extruded polyethylene. The intent of this study was to confirm that molded polyethylene and polyethylene radiated in inert environments reduce wear rates in vivo, to determine the combination of methods with the least wear, and to determine how much variance in wear is attributable to these methods. We reviewed 150 consecutive total hip arthroplasties done in 133 patients using 28-mm cobalt-chrome femoral heads and polyethylene-lined, titanium, ring-locked acetabular components. The least wear occurred in gamma inert-molded polyethylene components. The mean volumetric wear rates were 52.12 mm3/year for gamma inert-molded, 62.32 mm3/year for gamma inert-extruded, and 66.09 mm3/year for gamma air-extruded polyethylene components. Relative risk assessment found gamma air-extruded and gamma inert-extruded polyethylene components to wear 16% and 11% more than gamma inert-molded polyethylene components, respectively. Gender, body mass index, and age accounted for the greatest amount of the explained variance in volumetric wear (57.5%, 21.6%, and 14.4, respectively), followed by angle of wear (3.4%), and sterilization and production technique (3.2%).

Acetabulum↗

PubMed2005

Biodegradation of polyethylene by the thermophilic bacterium Brevibacillus borstelensis.

AIM: To select a polyethylene-degrading micro-organism and to study the factors affecting its biodegrading activity. METHODS AND RESULTS: A thermophilic bacterium Brevibaccillus borstelensis strain 707 (isolated from soil) utilized branched low-density polyethylene as the sole carbon source and degraded it. Incubation of polyethylene with B. borstelensis (30 days, 50 degrees C) reduced its gravimetric and molecular weights by 11 and 30% respectively. Brevibaccillus borstelensis also degraded polyethylene in the presence of mannitol. Biodegradation of u.v. photo-oxidized polyethylene increased with increasing irradiation time. Fourier Transform Infra-Red (FTIR) analysis of photo-oxidized polyethylene revealed a reduction in carbonyl groups after incubation with the bacteria. CONCLUSIONS: This study demonstrates that polyethylene--considered to be inert--can be biodegraded if the right microbial strain is isolated. Enrichment culture methods were effective for isolating a thermophilic bacterium capable of utilizing polyethylene as the sole carbon and energy source. Maximal biodegradation was obtained in combination with photo-oxidation, which showed that carbonyl residues formed by photo-oxidation play a role in biodegradation. Brevibaccillus borstelensis also degraded the CH2 backbone of nonirradiated polyethylene. SIGNIFICANCE AND IMPACT OF THE STUDY: Biodegradation of polyethylene by a single bacterial strain contributes to our understanding of the process and the factors affecting polyethylene biodegradation.

Bacteriological Techniques↗

PubMed1994

Parallel determination of gut permeability in man with M(r) 400, M(r) 1500, M(r) 4000 and M(r) 10,000 polyethylene glycol.

Polyethylene glycol has been in use for a number of years for the assessment of gut permeability. The methods so far employed are usually limited to polyethylene glycols in the low relative molecular mass range (up to M(r) 1300). We developed a method for the simultaneous determination of gut permeability to M(r) 400, M(r) 1500, M(r) 4000 and M(r) 10,000 polyethylene glycol, by applying a single oral dose of an appropriate mixture of these polyethylene glycols. After extraction from 24 h-urine, M(r) 1500, M(r) 4000 and M(r) 10,000 polyethylene glycol were quantified by size exclusion chromatography, while M(r) 400 polyethylene glycol was determined by reversed phase chromatography. The detection limit of polyethylene glycol in the relative molecular mass range between M(r) 1500 and M(r) 10,000 was found to be 0.2 mg/l urine, and the detection limit of M(r) 400 polyethylene glycol 5 mg/l urine. Recovery of the polyethylene glycols (N = 6) were 86.6% (CV: 4.8%) for M(r) 400, 94.1% (CV: 7.2%) for M(r) 1500, 97.1% (CV: 5.5%) for M(r) 4000 and 97.4% (CV: 5.6%) for M(r) 10,000. No significant difference was found between the excretion rates in 24 h-urine of M(r) 400 and M(r) 1500 polyethylene glycols in patients with Crohn's disease (M(r) 400: 34.4 +/- 5.5%; M(r) 1500: 5.22 +/- 2.27%; mean +/- SEM, N = 10) and healthy controls (M(r) 400: 33.6 +/- 3.2%, M(r) 1500: 1.09 +/- 0.26%; N = 21). The excretion rate of M(r) 4000 polyethylene glycol was markedly higher in patients with Crohn's disease (0.462 +/- 0.177%) than in healthy controls (0.049 +/- 0.012%, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2003

[Early failure of the polyethylene liner in the ABG I total hip prosthesis].

PURPOSE OF THE STUDY: The polyethylene liner has appeared to be a weak point in total hip arthroplasty. An early wear-through or a fracture of the polyethylene liner have been referred to as a catastrophic failure. The aim of the present study is to report our experience with this rare complication in ABG I hip prostheses. MATERIAL: Between September 1994 and January 2000 a total of 506 ABG I prostheses were implanted at our clinic. Due to wear-related complications, revision arthroplasty had to be performed in 90 hips in 23 male and 63 female patients by January 2002. Extensive titanium metallosis associated with polyethylene failure was found in 11 hips of 11 female patients. The remaining 56 hips of 52 female patients served as a control group. METHODS: The characteristics recorded in every patient's included age, type of patient, sex, height, weight, ESR, CRP, diagnosis, Harris hip score before revision, cup size, abduction angle of the cup, time between the primary and revision surgery and implant stability. Student's t-test, the Mann-Whitney U-test and Pearson's chi 2 test were used to evaluate the results. RESULTS: The complete failure of ABG I prostheses occurred in 2.17% of the replaced hips (11/506). A fracture or complete wear-through were the causes of failure in three (3/11, 27%) and eight (8/11, 73%) hips, respectively. The average cup size in hips without metallosis was 48.9 mm (range, 44-58; SD, 3.1) and that in hips with metallosis was 46.5 mm (range, 46-48; SD, 0.9). This difference was highly significant (t-test, p = 0.00002; U-test, p = 0.014). In the hips with metallosis, the average thickness of the polyethylene liner was 5.17 mm (range, 4.9-5.9; SD, 0.45) and the Harris hip scores before revision were significantly lower than in the hips without metallosis (59 versus 70.3 points; t-test, p = 0.023; U-test, p = 0.044). There were no other significant differences between the hips with early catastrophic failure of the polyethylene liner and those without it. DISCUSSION: Several studies have shown an indirect relationship between polyethylene thickness and its wear. Berry et al. reported catastrophic failure in hip prostheses with a polyethylene thickness of less than 5 mm; in our study, the three failed polyethylene liners were 5.9 mm in thickness. CONCLUSIONS: This is the first report on a wear-through of the polyethylene liner in ABG I cups. It is suggested that a thin polyethylene liner, design characteristics and probably also poor polyethylene quality are crucial factors responsible for rapid wear in ABG I cup. The highest risk is associated with the combination of a 46 mm cup and a 28 mm head. Patients who have prostheses of this size should be checked up more frequently.

Adult↗

PubMed2004

Knee simulator wear of polyethylene tibias articulating against explanted rough femoral components.

Highly cross-linked and melted polyethylene tibial inserts have recently been introduced for clinical use to reduce fatigue damage and adhesive wear in tibial inserts. Other authors have studied the effect of counterface roughness on the wear behavior of polyethylene tibial inserts in knee simulators using femoral components that were roughened artificially. They reported a higher wear rate with highly cross-linked polyethylene than with unirradiated polyethylene tibial inserts. Artificial roughening of femoral components may not be clinically relevant. To evaluate this concern, we studied the wear behavior of highly cross-linked and conventional polyethylene tibial inserts articulating in vitro against surgically retrieved femoral components that had become roughened in vivo. The wear rate of the highly cross-linked polyethylene (5.9 and 6.8 mg/1 million cycles with 100 and 50% serum) was 80% lower than the wear rate of the conventional polyethylene (33.5 and 32.2 mg/1 million cycles with 100 and 50% serum) tibial inserts after 2 million cycles of simulated gait. This study suggests that during in vivo use, scratches that are generated on the femoral components are likely to produce a higher wear rate with both cross-linked and conventional polyethylene than a smooth femoral component, but that this wear rate is likely to be higher with conventional polyethylene than with highly cross-linked polyethylene tibial inserts.

Femur↗

PubMed2001

Intracellular measurement of polyethylene particles. A histomorphometric study.

A histological and histomorphometric study was carried out on pseudo-capsules retrieved from patients during revision surgery of cementless total hip replacement. Polyethylene loading and areal polyethylene particle size in different cells of the reticuloendothelial cell line were determined within the tissue by histomorphometry. In the reticuloendothelial cell line, foreign-body giant cells are considered to be the result of confluence of mononuclear macrophages caused by large particles or other unknown stimuli. The aim of this study was to investigate whether polyethylene particle size and polyethylene loading are different in mononuclear macrophages and foreign-body giant cells. The specimens were examined under the light-optical microscope with plain and polarized light. The polyethylene loading of 329 macrophages (mononuclear), 81 small foreign-body giant cells (2-5 visible nuclei), and 103 large foreign-body giant cells (6 or more visible nuclei) was determined and the intracellular polyethylene particle size analyzed by histomorphometry. The mean polyethylene loading was 13 +/- 8 microm2, 25 +/- 16 microm2, and 49 +/- 42 microm2, respectively. This difference was statistically significant (Student's t-test, P < 0.05). The mean polyethylene particle size was 2.34 +/- 3.2 microm2, 3.02 +/- 3.46 microm2, and 4.70 +/- 11.25 microm2, respectively. This difference was statistically significant between macrophages and large foreign-body giant cells (t-test, P < 0.05). The findings of this light-optical study show that the mean intracellular polyethylene particle size is greater in foreign-body giant cells. In addition, absolute polyethylene loading tends to be higher in foreign-body giant cells than in mononuclear macrophages.

Female↗

PubMed2006

The influence of povidone K17 on the storage stability of solid dispersions of nimodipine and polyethylene glycol.

Previous studies revealed that solid dispersions containing nimodipine and polyethylene glycol 2000 can be effectively prevented from recrystallization by adding povidone K17. These systems are characterized by a high dissolution rate and a remarkable supersaturation of the drug in the dissolution media. It is still unknown if these characteristics are achievable with all polyethylene glycol and povidone mixtures. The objective of the present study is to find out, whether povidone K17 has to be dissolved in melted polyethylene glycol during the preparation process of solid dispersions by the melting method in order to avoid recrystallization of the drug and to ensure storage stability. Solid dispersions consisting of 20% (m/m) nimodipine, 16% (m/m) povidone K17 and 64% (m/m) of six different mixtures of polyethylene glycol 2000 and 8000 were prepared by the melting method and investigated by dissolution testing, thermal analysis and X-ray diffraction. As the solubility of povidone K17 in polyethylene glycol 2000 is about 70% at 65 degrees C and decreases with increasing molecular weight of the polyethylene glycol, mixtures containing different amounts of dissolved povidone K17 are obtained by varying the mixing ratio of polyethylene glycol 2000 and 8000. Recrystallization is inhibited in the formulations, containing mainly polyethylene glycol 2000 whereas recrystallization occurs in systems consisting predominantly of polyethylene glycol 8000. These results show clearly that dissolution of povidone in melted polyethylene glycol is a prerequisite in order to prevent recrystallization.

Calorimetry, Differential Scanning↗

PubMed1995

Effect of water-loading on the performance of polyethylene glycol as a marker of small intestinal permeability.

1. Polyethylene glycol has been used extensively to measure small intestinal permeability in vivo. However, polyethylene glycol seems to traverse the intestinal mucosa in much greater quantities than sugar molecules of equivalent M(r). In addition, the recovery of the lowest M(r) polymers of administered polyethylene glycol has been found to be both low and unreliable. 2. To compare the behaviour of a range of polyethylene glycol polymers with sugar probes in vivo, a combined polyethylene glycol/mannitol/lactulose probe was administered sequentially to healthy individuals in the fasted state and under conditions of water-loading. Timed hourly urine collections were made for 6 h. 3. Mannitol and lactulose recoveries were all within the normal range and were unaffected by co-administration of water. The lactulose/mannitol recovery ratios did not vary significantly over the 6 h collection period. In contrast, the recovery of total polyethylene glycol was significantly greater when subjects were water-loaded. Furthermore, proportionally greater quantities of polyethylene glycol M(r) 370 than M(r) 854 were recovered towards the end of the collection period than at the start. 4. Our results show that, in contrast to lactulose and mannitol, excretion of low-medium M(r) polyethylene glycol polymers is highly dependent on co-administration of water. Furthermore, the differential rate of excretion of the low compared with the high M(r) polyethylene glycol polymers suggests that the volume of distribution of the individual polymers may vary with M(r), and smaller polyethylene glycol molecules may undergo considerable renal tubular reabsorption.

Adult↗

PubMed2006

A randomized, prospective, comparison study of polyethylene glycol 3350 without electrolytes and milk of magnesia for children with constipation and fecal incontinence.

OBJECTIVE: Our aim was to compare 2 laxatives, namely, polyethylene glycol 3350 without electrolytes and milk of magnesia, evaluating the efficacy, safety, acceptance, and 1-year outcomes. METHODS: Seventy-nine children with chronic constipation and fecal incontinence were assigned randomly to receive polyethylene glycol or milk of magnesia and were treated for 12 months in tertiary care pediatric clinics. Children were counted as improved or recovered depending on resolution of constipation, fecal incontinence, and abdominal pain after 1, 3, 6, and 12 months. An intent-to-treat analysis was used. Safety was assessed with evaluation of clinical adverse effects and blood tests. RESULTS: Thirty-nine children were assigned randomly to receive polyethylene glycol and 40 to receive milk of magnesia. At each follow-up visit, significant improvement was seen in both groups, with significant increases in the frequency of bowel movements, decreases in the frequency of incontinence episodes, and resolution of abdominal pain. Compliance rates were 95% for polyethylene glycol and 65% for milk of magnesia. After 12 months, 62% of polyethylene glycol-treated children and 43% of milk of magnesia-treated children exhibited improvement, and 33% of polyethylene glycol-treated children and 23% of milk of magnesia-treated children had recovered. Polyethylene glycol and milk of magnesia did not cause clinically significant side effects or blood abnormalities, except that 1 child was allergic to polyethylene glycol. CONCLUSIONS: In this randomized study, polyethylene glycol and milk of magnesia were equally effective in the long-term treatment of children with constipation and fecal incontinence. Polyethylene glycol was safe for the long-term treatment of these children and was better accepted by the children than milk of magnesia.

Abdominal Pain↗

PubMed2000

Effect of sterilization method and other modifications on the wear resistance of acetabular cups made of ultra-high molecular weight polyethylene. A hip-simulator study.

BACKGROUND: Wear of ultra-high molecular weight polyethylene acetabular cups in hip prostheses produces billions of submicrometer wear particles annually that can cause osteolysis and loosening of the components. Thus, substantial improvement of the wear resistance of ultra-high molecular weight polyethylene could extend the clinical life span of total hip prostheses. It has become apparent that the conditions under which ultra-high molecular weight polyethylene cups have been sterilized can markedly affect their long-term wear properties, and new sterilization methods and other modifications have been developed to minimize the negative effects. METHODS: In the present study, a hip-joint simulator was used to assess whether it is preferable to sterilize ultra-high molecular weight polyethylene cups without gamma irradiation, to avoid radiation-induced oxidative degradation, or to sterilize with gamma irradiation while the cups are packaged in a suitable low-oxygen atmosphere to minimize oxidation while retaining the increased wear resistance conferred by the radiation-induced cross-linking. Ion-implanted cups and cups made of a highly crystalline polyethylene (Hylamer) also were investigated. Cups made of each material were subjected to wear-testing prior to and after artificial thermal aging to accelerate oxidative degradation. RESULTS: The results of the present study demonstrated that the cross-linking induced by gamma irradiation improves the wear resistance of ultra-high molecular weight polyethylene, while oxidation reduces it. Without thermal aging, the two types of cups that were sterilized with gamma irradiation while in low-oxygen packaging exhibited about a 50 percent lower rate of wear than did either the nonsterilized cups or the nonirradiated cups sterilized with gas plasma. There was a comparable advantage in the rate of wear after fourteen days of thermal aging. However, after thirty days of aging, the cups sterilized with gamma irradiation in low-oxygen packaging wore several times faster than did the nonirradiated cups. Ion-implanting improved the wear resistance without thermal aging, but after extensive thermal aging the oxidation and wear were greater than those of the controls. Hylamer cups (that is, those that were sterilized with gas plasma) exhibited wear properties very close to those of the nonsterilized ultra-high molecular weight polyethylene cups (the controls) with or without aging. CONCLUSIONS: Sterilizing an ultra-high molecular weight polyethylene acetabular cup without radiation (for example, with ethylene oxide or gas plasma) avoids immediate and long-term oxidative degradation of the implant but does not improve the inherent wear resistance of the polyethylene. Sterilizing with use of gamma irradiation with the implant packaged in a low-oxygen atmosphere avoids immediate oxidation and cross-links the polyethylene, thereby increasing its wear resistance, but long-term oxidation of the residual free radicals may markedly reduce the wear resistance. Ideally, cross-linking with gamma irradiation to reduce wear should be done in a manner that avoids both immediate and long-term oxidation.

Acetabulum↗